Stenosis aortic

The pathogenesis of disorders of blood circulation.
Stenosis aortic at narrowing of, resulting from the fusion between the semilunar valves aortic valve in the field of commissures, creates an obstacle to the outflow of blood during systole from the left ventricle into the aorta. The cross-sectional area of the normal aortic holes in the adult averages 3 - 3.2 cm2, the circle 7,5 cm, hemodynamic disorders occur when the smaller opening to 0.9 - 0.7 cm2 (G. I. Tsukerman et al., 1972), in patients With severe stenosis size of the holes may be reduced to 0.5 cm2, and the circumference of up to 2 cm (C. X. Vasilenko, 1972). For emptying the left ventricle during systole he has to make more than in normal conditions, work, so developing systolic left ventricular overload leading to hypertrophy of his muscles. In the developed muscle hypertrophy of the left ventricle minute volume large circulation for a long time remains normal (C. S. Saveliev, 1959).
Overcoming the resistance during the ejection of blood through narrowed aortic hole leads to changes in the duration of phase beats, thus extended period of exile (G. F. lang, 1958). Systolic pressure in the cavity of the left ventricle is significantly increased, reaching sometimes digits 250-300 mm RT. Art., but because a large amount of energy is spent on overcoming the blood obstacles, in the aortic systolic pressure is clearly reduced, there is so-called gradient (difference) pressure between the left ventricle and the aorta. Moderate stenosis pressure gradient can be 20-50 mm RT century, with severe - to 50 - 100 mm RT. century (B. X. Vasilenko, 1972).
The systolic pressure in the cavity left ventricular leads to disorders (decrease) in coronary blood flow. At the same time, exaggerated muscle of the left ventricle requires a special coronary blood flow. This discrepancy between coronary blood flow and the needs of the hypertrophied infarction creates conditions for development in aortic stenosis of coronary insufficiency.
In contrast to the failure of the aortic valve, which is a combination of dilatation of the left ventricular cavity with hypertrophy of its walls, for aortic stenosis characterized by the development of left ventricular hypertrophy without expanding its cavity or extension expressed very little (Fig. 23). Only when decreasing the contractile ability of the left ventricle develops its dilation and insufficiency of blood circulation in a small circle.